external_entities-8.x-2.x-dev/external_entities.links.menu.yml

entity.external_entity_type.collection:
  title: 'External entity types'
  parent: system.admin_structure
  description: 'Create and manage fields, forms, and display settings for your external entity types.'
  route_name: entity.external_entity_type.collection

system.external:
  route_name: system.external
  parent: system.admin_config
  title: 'External data'

system.external_entities:
  title: 'External entities'
  parent: system.external
  description: 'List and configure external entities.'
  route_name: entity.external_entity_type.collection